Method and means of repairing a pipe

ABSTRACT

The invention relates to a permanent method of repairing leaking, damaged or weakened pipe by grit blasting the pipe ( 10 ), followed by wrapping it with a fibre reinforced composite material ( 12 ), then installing two half oversized steel sleeves ( 14 ). After that the non-gaseous matter is removed by fresh water and compressed air or inert gas. An epoxy or cementitious grout or a combination of both is finally injected into annular chamber ( 20 ) of the sleeves through pre-installed inlet port ( 16 ) and outlet port ( 18 ). The epoxy or cementitious is then allowed to cure. The means to seal the terminal end of steel sleeves includes a pair end flanges ( 32 ) matingly securable to a pair of terminator bodies ( 45 ).

[0001] The invention relates to a method and means of repairing a pipemore particularly the invention relates to a method and means ofrepairing a damaged pipe without isolating the pipe or without stoppingthe flow of materials within the pipe.

[0002] When pipe repairs are to be carried out, three main repairscenarios are normally encountered. This will include (i) pipes subjectto external metal loss (caused by corrosion or mechanical damage), (ii)pipes subject to internal metal loss (caused by corrosion, erosion orerosion/corrosion) and (iii) piping components that are leaking. Inaddition to these main repair scenarios, the extent of the deteriorationor damage (i.e. localized or extensive) has also to be considered whenchoosing the repair methods and repair components.

[0003] Current repair methods include clamps (localized repairs) andspecialized connectors with sleeves (extensive repairs). It is equallypossible to encircle the detective area with close fit metallic sleeveswhich are welded together. This, however, has to be seal welded. Thesemethods could cause weld induced damage or material property chances onthe pipe being repaired. In underwater conditions this may requirespecialist habitats to carry out hyperbaric welding. This can provecostly and can pose additional dangers. Welding on live pipelines posesfurther additional dangers.

[0004] Condition and extent of damage of the pipe essentially dictatesthe type of repairs to be carried out. If the external surface isdamaged to the extent that an elastomeric seal cannot provide sufficientsealing forces in the immediate vicinity of the damage, or in therelatively unaffected areas adjacent to the major damage (these areasbeing used to effect the sealing forces of ‘stand’-off repair clamps),the external pipe surface may need to be re-installed using some form offiller material. Developments using epoxy-filled steel sleeves have beenshown to accommodate such areas of extensive damage and haveapplications for a whole range of defects including corrosion,non-propagating cracks, dents or gouges in both axial andcircumferential orientation, and girth weld associated anomalies. Theepoxy-filled sleeve repair technique is typically recommended on areasoperating below 100 barg with temperatures not exceeding 100° C. It wasassumed that epoxy filled sleeves can be used for leak containment.However in various tests conducted it has been found that the sleeveswere only able to contain leaks below 40 barg. Additional tests wereconducted to determine if pumping epoxy and allowing it to cure underpressure i.e. 11 equilibrium pressure (to that within the pipe) wouldproduce better results. The tests prove that higher pressures areobtained but in practical terms this will involve de-rating the pipe orsuspending production and could prove costly for operators. There is aneed therefore to develop a method where the pipes can be repairedwithout de-rating the pipe or suspending the throughput of the pipe.

[0005] The prior art method is expensive in that heavy duty connectorsdimensioned to fit the damaged pipes, need to be provided. Suchconnectors are expensive and take substantial man-hours to design,manufacture and assemble. The prior art composite fibre wraps ethich hasa pressure limit not exceeding 40 barg. When the axial pressure exceeds40 barg or when used in isolation are considered temporary repairs.

[0006] The invention discloses a permanent method of repairing orreinforcing a weakened area in a pipeline section. The method includesremoving rust, old coating and other unwanted surface blemishes by gritblasting. Then the leaking, damaged or weakened surface are wrapped withat least one layer of reinforced composite wrap material. The compositewrap is left to cure. If necessary, to further mechanically strengthenthe affected portion of the pipeline, the pipeline in the affected areasis encapsulated by sleeves. Optionally, a wear plate can be placedbetween the affected portion of the pipeline and the composite wrapmaterial. Two half oversized steel sleeves are installed over the pipesection and bolted together or seal welded together and thus forming anannular chamber. Non gaseous matter in the annular chamber is removed byflushing with fresh water and followed by flushing with inert gas oratmospheric air. Load bearing epoxy or cementitious grout with highcompressive strength in excess of 100 Mpa or a combination of bothseparated by chambers is then introduced into annular chamber. Finallythe grout/combination of grout is allowed to cure. The above inventionis used for pipelines submerged in water or sea. Alternatively the samemethod can be done for pipelines on land except the procedures aremodified where by the two half oversized steel sleeves can be weldedtogether and the flushing with fresh water will no longer be required.The unwanted matter can be flushed out using compressed air or inertgas.

[0007] In another aspect, the invention discloses a means to seal theterminal ends of the two half oversized sleeves, positionable on theexternal circumferential side of affected riser pipes. The meanscomprises of a pair of flange bodies integral to the two half oversizedsleeves and a pair of terminator bodies. Each flange body includes asemi-circular collar with a plurality of bores thereon and asemi-circular lip. The terminator body includes a semi-circular collarwith a plurality of bores thereon, and a semi-circular recess structuredand configured to receive the semi-circular lip. A graphite body isintroduceable into the semi-circular recess. The terminator body issecured against the flange body by tightening of nuts and boltsintroduced between the bores (apertures) in the flange body and theterminator body.

[0008] In another aspect, the flange ends of the two half oversizedsteel sleeves are serrated along the longitudinal axis and sheets ofPTFE body is placed between the two steel sleeves before the steelsleeves are bolted together by nuts and bolts.

[0009] The invention will be described in reference to a preferredembodiments of the invention with reference to the following diagrams:

[0010]FIG. 1 shows a leaking, damaged or weakened surface area and thearea beyond the leaking, damaged or weakened surface portion of pipelineis to be grit blasted.

[0011]FIG. 2 shows a leaking, damaged or weakened surface area wrappedwith fibre reinforced wrap.

[0012]FIG. 3A shows longitudinal cross-sectional views of a pipe beingrepaired with a wear plate and wrap around fibre reinforced wrapped.FIG. 3B shows a cross sectional view of pipe in FIG. 4.

[0013]FIG. 4 shows an enclosure of the surface area with two halfoversized steel sleeves with inlet and outlet port. (Details of boltsand nuts or welds not shown).

[0014]FIG. 5A shows diagrammatic longitudinal and cross-sectional viewsof a pipe being repaired with a wear plate (optional) wrapped aroundfibre reinforced wrap, enclosed in sleeves with annular chamber filledwith grout.

[0015]FIG. 6 shows a cut away perspective view of a pipe being repairedwith half sleeves and terminating means

[0016]FIG. 7 shows a radial cross-sectional view of the pipe shown inFIG. 6.

[0017]FIG. 8 shows a detailed partial sectional view of the seal wingsof the sleeves.

[0018]FIG. 9 shows a sectional view of the terminating means.

[0019]FIG. 10 shows details of graphite ring splice.

[0020] The surface of a damaged/deteriorated pipe (20) is prepared firstby grit blasting to remove rust and remnants of old coating. Gritblasting is known as one of abrasive blasting. The blasting of the pipe(20) is carried out by sweep blasting using fine abrasives notcontaining iron (e.g. garnet, aluminum oxide), glass pearls or stainlesssteel shot. Maximum speed and most effective cleaning is obtained bysystematic blasting. Work is blocked out in 30 cm squares and eachsquare blasted evenly until complete. A minimum of 25 mm into anyadjacent coated area is continued by blasting and the edges arefeathered.

[0021] Then the thinned down, leaking or affected area is wrapped aroundwith a fibre reinforced composite wrap (21) capable of curing underwater and standing pressure. Example of a wrap is a fiberglass clothpre-impregnated, with a resin that can be activated by salt or freshwater. (FIG. 2) Optionally, wear plates (23) can be used in addition tothe fiberglass wrappings to reduce the risk of damage due to corrosionand erosion. (see FIG. 3). The fiberglass as sourced is packaged in ahermetically sealed foil pouch, it is ready to use and does not requireany measuring or mixing. It has an initial settling time of only 30minutes (24° C.). Preferably the fiberglass should be spirally wrappedwith overlapping layers. The number of wraps depends upon the operatingpressure desired; the greater the pressure the more wraps. Once the wrapis cured, it is preferable to control blast to create an anchor patternfor the epoxy or grout to be subsequently injected.

[0022] The above described embodiment is acceptable for temporaryrepairs of affected riser pipes. To provide a more permanent solution, afurther strengthening of the affected area of the riser is required.

[0023] Two half oversized matingly engageable steel sleeves (22) arethen installed covering and extending to beyond the deteriorated part ofa pipe (26) (FIG. 5). The extension of the sleeves (22) beyond thedeteriorated part of the pipe is to cater for axial loads of thematerial transported within the pipe. The sleeves are welded or boltedtogether around and beyond the damaged/deteriorated or corroded area.When the sleeves are secured together by nuts and bolts, then onesurface of the flange of each sleeve is serrated all along one side ofthe length of the sleeves (see FIG. 8). A strip of PTFE is placedbetween the serrated surface before the sleeves are secured together.The ends of the sleeves are capped. The sleeves are with inlet (16) andoutlet (18) port at the ends. The sleeves are dimensioned to allow anannular chamber (25) between the original pipe (20) and the sleeves(22). Upon installation of the sleeves the ends are capped using eitherfast epoxy curing resins or elastomeric seals (27) which are compressedwhen the sleeves are bolted or welded together or secured by other knownmeans in the art.

[0024] The annulus gap typically will range from 12.7 mm to perhapsmaximum of 76.2 mm and will be dependent upon surface condition of theeffected area i.e. dents, weld protrusions, out of dimension pipe etc.The size of the annulus shall be calculated to provide sufficient sheerand axial load carrying capacity. In addition grout (29) can beformulated with additives or aggregates to either insulate the pipe(reduce thermal shock especially at the splash zone) or to reduceshrinkage of the epoxy. All ambient water present in the annular chamber(25) should be discharged by means of the application of compressed airor other inert gas with a pressure not exceeding 9.7 bar (140 psi)entering through the inlet port (16) and allowing discharge through theoutlet port (18). The maximum pressure stated is for indicative purposesonly and is dependent upon the capacity of the end seals.

[0025] Upon removal of all ambient water from the annular chamber (25)by means of compressed air or inert gas, the annular chamber (25) isflushed with fresh water. The fresh water is injected from the inletport (16) and allowed to exit at the outlet port (18). The fresh wateris pumped at a pressure not exceeding 9.7 bar (140 psi). The procedureis continued until complete discharge of all contaminants. Uponcompletion of the above, the fresh water is discharged by means ofintroduction of inert gas. This procedure is continued until allmoisture is discharged from the annular chamber (25). The pressure inthe annular chamber (25) during the injection of the inert gas shall notexceed 9.7 bar (140 psi).

[0026] Finally a load bearing grout capable of curing under water isthen injected into annular chamber (25) of the sleeves through thepre-installed inlet and outlet port (16, 18). The maximum injectionpressure shall not exceed 9.7 bar (140 psi).

[0027] Load bearing filler material used in this present invention iseither epoxy based or cementitious grout. The epoxy should have lowviscosity, designed for application with automatic meter, mix anddispense pressure injection equipment. The physical properties allow itsuse in applications requiring high load bearing strength and excellentadhesion under adverse application conditions. It should have a longworking life and low exotherm reaction (minimal heat generation duringcure that make it suitable for applications where a relatively largemass of adhesive is employed. Preferably the epoxy should have a highdegree of chemical and radiation resistance attainable in the ambienttemperature. The injected epoxy is left to cure in accordance withmanufacturer's recommendations.

[0028] The cementitious grout should have high compressive strength andshould be pumpable and similarly should be left to cure as permanufacturer's recommendations. The epoxy/grout completely integratesthe sleeves (22) and the existing pipe (20) providing additionalstructural reinforcement. The sleeves (22) isolate the pipe thuspreventing further external corrosion and being bonded to the pipe (20)further strengthens the pipe. The fibre reinforced wrap (21) containsleaks within corroded area and in conjunction with the load bearinggrout (29) contains the hoop stresses experienced by the pipe. The axialloads are contained by making sleeves longer than the affected area.

[0029] In another aspect of the invention, there is disclosed a pair ofend flanges integrally secured to the pair of matingly engageable steelsleeves and a pair of independent terminal flanges, which are matinglyengageable to the said end flanges (see FIG. 6). It will be appreciatedthat instead of terminal ends of the matingly engageable steel sleevesbeing sealed by means of curing resins or elastimeric Seals, metalflanges are used to provide more secure end sealing effect.

[0030] Referring to FIG. 6, there is shown a sectional view of ariser/pipeline (20) to which is secured a pair of half sleeve pipes(22). Each half sleeve pipe (22) is a diameter larger than the diameterof the intended riser/pipeline (20) which it is proposed to cover. Thehalf sleeve includes a flange (24) at the terminal edges, said flangeextending throughout the length of the half sleeve. Each of the halfsleeve pipes includes a longitudinal serrated strip (26) extendingthroughout the length. The longitudinal serrated strip is designed tosecure a longitudinal seal (28), such as an elastomeric seal (such asPTFE), copper seal or any other seal capable of being compressed betweenthe two half sleeves to prevent leakage of materials contained withinthe two half sleeves when assembled together. The flanges include aplurality of spaced apart apertures (28) to accommodate nuts and boltswhich are used to connect the two half sleeves.

[0031] Instead of the two half sleeves being secured together by meansof flanges (24), it is possible to secure the half sleeves by weldingalong the edges. In this embodiment, there is no need for flanges at thehalf sleeves, neither is there a need for longitudinal serrated stripson the flanges.

[0032] Each terminal end of each half sleeve includes an end-flange body(32) integrated with the rest of the half sleeve. The end-flange body(32) includes a semi-circular collar (34) with spaced apart apertures(36). It further includes two flange portions (38,44) co-planar to theflange (24) in the rest of the sleeve. The said flange (38) includesapertures (40) to accommodate nuts and bolts when securing theend-flange body (32) to its appropriate end-flange body of the matinglyengageable terminator body. Integral to the end-flange body issemi-circular lip (42) extending forward from the semi-collar (34).

[0033] The invention further includes a terminator body (45)structurally configured to be secured to the end-flange body (32). Theterminator body (45) is independent and comprises of two identicalhalves to be secured to the two end-flange bodies (32). Each terminatorbody (45) includes a semi-circular collar (46) with spaced apartapertures (48). It also includes two pairs of flanges (50, 52) each withan aperture (53). The flanges (50) are positioned in a manner such thattwo terminator bodies placed in mirror image to each other are securableto each other by nuts and bolts. The terminator body further includessemi-circular recess (54) dimensioned and configured to receive thesemi-circular lip (42) from the end-flange body (32).

[0034] The working of the end connector comprising of the end-flangebody and the terminator body will be described now. The half sleeve withthe end-flange body (32) is positioned on the pre determined position ofthe riser pipe (20). The longitudinal seals (28) are placed in positionalong the longitudinal serrated strips. A graphite ring (56) formed bytwo semi-circular graphite strips is placed in the semi-circular recess(54). Preferably the terminal edges of semi-circular graphite strips isobliquely cut to provide a more effective seal (see FIG. 10). Three mildsteel rings (60, 62, 64) are positioned adjacent to graphite ring. Therings are provided to prevent any extrusion of graphite whilecompressing the graphite seal to activate. The half sleeves and theend-flange bodies are secured together by nut and bolt means (oralternatively are welded together).

[0035] After positioning the graphite ring (56), the terminator bodies(45) are placed in registration with the end-flange bodies and arecompressed against the end-flange body to a desired compression value toactivate the graphite ring as a seal. The graphite ring will change itsshape during external compression and fill up voids and gaps if any inthat area. At the same time, the density of the graphite ring willincrease due to additional compression. The additional compression forcerequired to compress the graphite ring is calculated based on thegraphite manufacturer's recommendation and on field requirements. Itwill be appreciated that the terminator bodies (45) are compressedagainst and secured to the end-flanges by means of the plurality of nutsand bolts (58).

[0036] It will be appreciated that the provision of a semi-circularrecess and a matingly engageable semi-circular lip can be present in theflange body and in terminator body respectively instead as describedabove.

[0037] This invention is developed to solve problems presented by large,high temperature risers/pipes operating up to 100° C. or higher, causingthermal shock at the splash zone, failure of the protective coating; andthe resulting accelerated corrosion.

[0038] The purpose of the invention is to provide a cost effectivetechnology to repair and/or rehabilitate these pipelines/risersoperating at high pressures without suspending production, and to solvethe problems caused by the accelerated rates of corrosion.

[0039] The advantages of this invention are it does not requirede-rating of pipeline or suspending production; it does not requireexpensive heavy duty connectors to take the axial loads or to containleaks via seals normally incorporated within the connectors; does notrequire welding on the pipe to be repaired; and it overcomes thelimitations of epoxy sleeves and fibre reinforced wraps usedindependently.

[0040] The above invention is used for pipelines submerged in water orsea. Alternatively the same method can be done for pipelines on landexcept the procedures are modified whereby the two half oversized steelsleeves can be welded together and the flushing with fresh water will nolonger be required. The unwanted matter can be flushed out usingcompressed air or inert gas.

1) A method of repairing a leaking, damaged or weakened area in apipeline (20) section characterized in that the method includes: a)removing rust, old coating and other unwanted surface blemishes on theleaking, damaged or weakened surface area and the surface beyond theleaking, damaged or weakened surface portion of the pipeline (20); b)wrapping the leaking, damaged or weakened surface portion of thepipeline referred in step (a) above by having at least one layer ofreinforced composite wrap material (21); c) allowing the reinforcedcomposite wrap material (21) to cure; d) enclosing total surface areasreferred to in step (a) with two half oversized steel sleeves (22); e)sealing terminal annulus ends of sleeves; f) removing non-gaseous matterin annular chamber (25) formed by sleeves (20), pipe and seals formed instep (e); g) introducing a load bearing epoxy or cementitious grout (29)or a combination of both into the annular chamber (25); h) allowing theload bearing epoxy or cementitious grout to cure. 2) A method ofrepairing a leaking, damaged or weakened area in pipeline (20) sectionas claimed in claim 1 wherein in step (a) the surface areas are gritblasted. 3) A method of repairing a leaking, damaged or weakened area inpipeline (20) section as claimed in claim 1 wherein the reinforcedcomposite wrap material (21) consists of fiber reinforced materialpre-impregnated with a resin that can be activated by salt or freshwater for underwater applications or UV or catalyst cured for abovewater applications. 4) A method of repairing a leaking, damaged orweakened area in pipeline section as claimed in claim 1 wherein thereinforced composite wrap (21) is wrapped in a spiral manner on theexternal surface of the pipeline (20). 5) A method of repairing leaking,damaged or weakened area in pipeline section as claimed in claim 1wherein the one of the oversized steel (22) sleeves include an inletport (16) and outlet port (18) or wherein one of the oversized steelsleeve includes an inlet and other mating pair oversized steel sleeveincludes an outlet port. 6) A method of repairing leaking, damaged orweakened area in pipeline (20) section as claimed in claim 1 wherein theterminal annulus ends are sealed by either using a fast curing resin orelastomeric material to form a hermetic seal. 7) A method of repairingleaking, damaged or weakened area in pipeline (20) section as claimed inclaim 1 wherein in step (f) the non-gaseous matter includes water or seawater. 8) A method of repairing leaking, damaged or weakened area inpipeline as claimed in claim 1 wherein the non-gaseous matter is removedby flushing the non-gaseous matter with fresh water followed by flushingwith inert gas or atmospheric air. 9) A method of repairing a leaking,damaged or weakened area in pipeline (20) as claimed in claim 1 whereinat least one wear plate (23) is placed between the pipeline (20) and thereinforced composite wrap material (21). 10) A method of repairing aleaking, damaged or weakened area in pipeline (20) as claimed in claim 1wherein the terminal annulus ends are sealed by hermetically securing apair of terminator bodies (45) to a pair of flange bodies (32), saidflange bodies integral to the two half oversized steel sleeves (20). 11)A method of repairing a leaking, damaged or weakened area in pipeline(20) as claimed in claim 10 wherein two semi-circular graphite bodies(56) with angular cut terminal ends are introduced between the pair ofterminator bodies (45) and the pair of flange bodies (32) to form acircular ring. 12) A method of repairing a leaking, damaged or weakenedarea in pipeline (20) as claimed in claim 10 wherein the pair ofterminator bodies (45) are compressed against the pair of flange bodies(24) by means a plurality of nuts and bolts (58). 13) A method ofrepairing a leaking, damaged or weakened area in pipeline (20) asclaimed in claims 12 and 13 wherein a plurality of metallic rings (60,62, 64) are placed along the peripheral surface of the graphite bodies(56) now formed into a circular ring to prevent any extrusion of thegraphite when compressed. 14) A means to seal terminal end of two halfoversized sleeves (22) positionable on the external circumferential sideof pipes (20) comprising of a pair of flange bodies (24) and a pair ofterminator bodies (45) wherein the flange bodies (24) are integral tothe two half oversized sleeves (22); wherein each flange body (24)includes a semi-circular collar (34) with a plurality of bores (40)thereon, a wing with an aperture and a semi-circular lip (42); whereineach terminator body (45) includes a semi-circular collar (46) with aplurality of bores (48) thereon, a wing with an aperture semi-circularrecess (54) dimensioned and configured to receive the semi-circular lip(42); and wherein two semi-circular graphite bodies (56) areintroduceable into the semi-circular recess (54) and two flange bodiesand the two terminator bodies are securable together and the terminatorbody (45) is thereafter securable against the flange body (24) by thetightening of nuts and bolts introduced between the bores (36, 48) onthe flange body and terminator body. 15) A means to seal the terminalend of two half oversized sleeves as claimed in claim 14 wherein each ofthe two oversized sleeves includes on each side a flange (24) withserrated strip (26). 16) A means to seal the terminal ends of two halfoversized sleeves as claimed in claim 14 wherein terminator bodiesinclude a semi-circular lip instead of a semi-circular recess, and theflange bodies include a semi-circular recess instead of a semi-circularlip. 17) A means to seal the terminal ends of two half oversized sleevesas claimed in claim 14 wherein a graphite strip (56) is introduceablewithin the semi-circular recess (54). 18) A means to seal the terminalends of two half oversized sleeves as claimed in claim 14 wherein atleast one circular metallic clip is positionable in contact with the twosemi-circular graphite bodies to prevent leakage of graphite outside theterminator bodies when subjected to compression pressure. 19) A means toseal the terminal end of two half-oversized sleeves as claimed in claim15 wherein a strip of teflon (PTFE) is placed between the serratedstrips (26) before the flanges are secured by nuts and bolts.